For more than four decades Charles Wheeler, who has died aged 85, reported for radio and television from most of the world's trouble spots, becoming in the process the BBC's longest-serving foreign correspondent.

Though his craggy features and shock of white hair were his most obvious trademarks, they were incidental to an investigative skill and sense of judgment which made him one of the most authoritative reporters of his generation.

Wheeler was the son of an RAF wing commander who by the late 1920s was an expatriate employee of a Bremen shipping company. Moving to Hamburg, one of Wheeler's early formative experiences was to observe the violence that brought the Nazis to absolute power. He was sent to Cranbrook school in Kent and by the time he left at 17, Britain was at war with Germany. While waiting to join the services, Wheeler took a job in 1940 as a copy boy at the tabloid Daily Sketch, sparking off a lifelong taste for journalism.

In 1942 he went into the Royal Marines and with the rank of captain was assigned to a special unit created by the author Ian Fleming to gather advance intelligence for the D-day landings in June 1944. He was selected because of his fluent German but made such an impression on his unit commander, Patrick Dalzel-Job (on whom Fleming reputedly based James Bond) that he was rapidly promoted to second-in-command. His fellow officers described him as cheerful, efficient and very brave. After the war he was posted to Berlin, helping some of Germany's submarine commanders flee the eastern provinces.

On demobilisation in 1947, he joined the BBC's External Service, initially as a sub-editor and later as its Berlin correspondent. From there he reported on the gradual emergence of West German democracy, and the parallel clampdown on dissidence in the east of the communist German Democratic Republic. But, after three years and over his own protests, he was brought back to London to serve as a talks writer.

Increasingly frustrated by this desk work he decided to move to television in 1956, when Panorama offered him a job as a producer. But, as he was the first to acknowledge, the nitpicking imperatives of production did not enthral him (he was notorious for his indifference to deadlines) and, after two years, he moved to New Delhi as the BBC's South Asia correspondent.

Among the stories he covered was the Dalai Lama's flight from Tibet in 1959. But these were the closing years of the rule of prime minister Jawaharlal Nehru, whose capacity to handle his turbulent nation was diminishing rapidly. Though Wheeler's reporting was generally sympathetic, the robust terms in which it was sometimes couched drew periodic official protests. The greatest furore came after a trip to Ceylon (which became Sri Lanka in 1972), where the government threatened to leave the Commonwealth after Wheeler had called its prime minister "an inexperienced eccentric at the head of a cabinet of mediocrities". The British prime minister, Harold Macmillan, was forced to issue a public apology to defuse the crisis.

In 1962 Wheeler went back to Berlin, by now more concretely divided by the wall erected by the GDR. Once again, he had arrived for the closing years of an ancien regime, and the architect of West Germany's postwar recovery, Konrad Adenauer, had been allowed to remain in the post at the age of 86 on the bizarre condition that he retire by the time he was 90. During the old man's frantic final attempts to complete his political monument, Wheeler did his best to convey the significance of what was happening to a British mass audience.

It was hard material for any reporter to shape and the absence of background knowledge generated a complete lack of interest among most listeners: it usually needed something like a spectacular escape across the wall to rouse a flicker of attention, so it was probably with some relief that Wheeler packed his bags in 1965 to move to Washington.

As in most professions, luck played its part. Wheeler took up his new posting just as America was becoming the world news centre. President Lyndon Johnson's civil rights legislation, having raised black expectations, seemed unable to meet them at anything like an acceptable pace.

Wheeler found himself criss-crossing the country — from voting protests in Alabama, to anti-segregation marches in Chicago, to the devastating riots in the Watts area of Los Angeles in which 34 people died. In a succession of memorable reports he not only dealt with the spot news but sent interviews and background research which gave a British audience a much clearer understanding.

He also found himself in the midst of the rapidly accelerating opposition to the Vietnam war and the radicalisation of America's universities. Night after night he chronicled first the protest movement that drove Johnson from the White House and then the divisive campaign that irreparably split the Democratic party and brought Richard Nixon to the presidency in the 1968 elections. It made him one of broadcasting's best-known names and voices.

His observation of Nixon in office tended to confirm the view he had formed of him as vice-president years before: when guiding him on a tour of Berlin he found him "weird and totally mad". This judgment was confirmed during the 1972 Republican convention when Wheeler was inadvertently given a copy of the minute-by-minute stage management of the President's renomination, even down to the length of the spontaneous applause. Firmly resisting all official efforts to stop him, he gave a hilarious precis of the arrangements to that evening's viewers.

It should have been a warning of the sequence of dirty tricks and illegalities that was to become the Watergate scandal. News desks in Britain and the rest of Europe were curiously late waking up to the dimensions of the issue, and to a degree their attention was eventually caught by the reports Wheeler sent back. Not least of his professional skills was to hone what was, even for Americans, a fairly incomprehensible issue into a pithy summary.

But Wheeler did not stay to see Nixon forced from office. With Britain's accession to the European Economic Community in 1973 he became European correspondent. In February 1974 Harold Wilson's Labour party was returned to power and Wheeler found himself trying to explain the government's endless haggling over the size of Britain's contribution to the community budget. After a massive affirmative vote in the 1975 referendum, public interest in Europe soon dwindled, and Wheeler rejoined Panorama in 1977.

This was the format best suited to his journalistic style. It allowed him sufficient preparation and a long enough segment to give the viewer a carefully considered and stylish perspective. And Wheeler's on-screen presence, simultaneously professorial and incisive, was perfectly suited to this more analytical approach. He could, at times, be a ferocious interviewer, politely refusing to let the victim evade or obfuscate.

It may have been this quality that persuaded the BBC he would be the ideal presenter for Newsnight when it started in 1980. It was hopeless, and his distaste for the apparent omniscience required of a frontman was evident. The assignment ended in tears when, in the middle of some mammoth technical disaster, Wheeler told the audience he had no idea what was going on and simply sat mutely while it was sorted out. He was, as he later acknowledged, quite rightly sacked.

This was to the benefit of both BBC and viewers. It put him back on the road for Newsnight, among others. His reports soon came rolling in from the disintegrating Soviet Union, the Berlin Wall, the Gulf War, Kurdistan, and almost anywhere that suffering humanity needed a concerned and effective witness. Over the years his documentaries included the Kennedy Legacy (1970), Battle for Berlin (1985), the Legacy of Martin Luther King (1993) and Coming Home (2006). In 1955 his book, The East German Rising, co-written with Stefan Brant was published.

As the reports accumulated so they attracted well-earned professional recognition. His many awards included Journalist of the Year (1988) from the Royal Television Society, its International Documentary Award (1989) and a special commendation (1992). The Broadcasting Press Guild presented him with its Harvey Lee Award (1995) and made him television journalist of the year in 1996. He became an honorary doctor at the Open University and in 2006 he was knighted.

He was twice married. In 1962 he married Dip Singh, who survives him, as do his two daughters, Marina, a barrister married to Boris Johnson, the mayor of London, and Shirin, who works for the BBC.